High in the mists of the Welsh mountains lurked ferocious creatures hunting human flesh and blood. The Lewis family had hand reared a pair of baboons which lived with them for several years in their remote home. Then came the 1976 Dangerous Wild Animals Act which demanded costly security to be installed. They could no longer afford to keep their pets so they secretly released them in the Welsh Mountains. Nothing more was seen of the primates but they had reared their young, hidden from humans, in the vast forests and mountain mists. Then, forty years later, the killings began and the mountains became a dangerous place for climbers and walkers.